Polyolefins are widely used in a number of everyday articles, machines, consumer goods, and the like. Polyolefins are relatively inexpensive to produce and are capable of providing a number of useful functions. Polyolefins may be formed into various shapes, films, laminates, and the like. Polyolefins may be coated on, or co-extruded with various substrates. Polyolefins may also be combined with other materials to form a structure having a plurality of layers, each layer having a specific purpose. Laminates, for example, may comprise a plurality of layers, such as a configurationally rigid core layer, an outer liquid-tight layer, an oxygen gas barrier such as a mid-layer of aluminum foil, and/or other layers depending on application needs.
However, polyolefins may have relatively high glass transition temperatures. This may render various polyolefins brittle, inflexible, and thus unsuitable for particular uses, particularly uses at lower temperatures. Many applications of polyolefins would benefit from a polyolefin having useful properties over a wide range of temperatures, and under a variety of conditions. Such useful properties may include both high and low temperatures performance in the areas of impact strength, toughness, flexibility, and the like. One way in which such properties may be obtained is by the addition of plasticizers to polyolefins.
Examples of the addition of plasticizers to polyolefins may be found, for example, in U.S. Pat. Nos. 4,960,820, 4,132,698, 3,201,364, and in WO 02/31044, WO 01/18109, and EP 0 300 689. These and other references are directed to the addition of functionalized plasticizers to polyolefins. Examples of functionalized plasticizers include mineral oils containing aromatic groups. These exampled fail to provide improvements in impact strength, transparency, and other properties of polyolefins. Other references which are directed to the addition of plasticizers to polyolefins include EP 0 448 259, EP 1 028 145, U.S. Pat. Nos. 4,073,782, and 3,415,925.
It would be desirable to utilize compounds such as paraffins to plasticize polyolefins. However, such an approach is taught to be counter to producing improved polyolefins (See e.g., Chemical Additives for Plastics Industry 107-116 (Radian Corp., Noyes Data Corporation, NJ 1987); and WO 01/18109 A1.)
U.S. patent application Ser. No. 10/716,306, filed Feb. 19, 2004 is directed to a plasticized polyolefin composition comprising one or more polyolefins and one or more non-functionalized plasticizers. The plasticized polyolefins produced are reported to comprise improved softness, better flexibility (lower flexural modulus), a depressed glass transitions temperature, and/or improved impact strength when compared to plasticized polyolefins known in the art.
However, a need remains for facile incorporation of plasticizers into polyolefins. Plasticizers are often liquids. On the other hand, polyolefins are typically formulated, compounded, and/or combined as solids or partially molten semi-solids in extruders, mixers, kneaders, and the like. Such processes are not readily amenable to addition of liquids. Addition of liquids to an extruder, for example, may require utilization of metering pumps and extruder configurations in opposite to those useful to produce polyolefin articles of commerce. Accordingly, there remains a need for a method by which plasticizers may be incorporated into polyolefin compositions wherein the plasticizers are in a solid form that is flowable.